In recent years, from the viewpoint of space saving, there have been widely used flat panel displays such as a liquid crystal display, a plasma display, an OLED display, and a field emission display, in place of a CRT type display which is conventionally widely used. Further reduction in thickness is demanded for those flat panel displays. In particular, it is required that the OLED display be easily carried by being folded or wound and be usable not only on a flat surface but also on a curved surface. Further, uses on both flat surfaces and curved surfaces are not limited to only display devices. For example, if a solar cell or an OLED lighting device can be formed on a surface of an object having a curved surface, such as a surface of an automobile body, or a roof, a pillar, or an outer wall of a building, the applications thereof may expand. Substrates and cover glasses used for those devices are therefore required to be made thinner and to have high flexibility.
An illuminant used for an OLED display deteriorates in quality through contacting with gasses such as oxygen and water vapor. Thus, a substrate used for the OLED display is required to have high gas-barrier property, and hence the use of a glass substrate for the substrate is expected. However, glass used for a substrate is weak in tensile stress unlike a resin film, and hence is low in flexibility. Thus, application of a tensile stress on a surface of a glass substrate by bending the glass substrate leads to the breakage of the glass substrate. In order to impart flexibility to the glass substrate, the glass substrate is required to be made ultrathin. Thus, a glass film having a thickness of 200 μm or less is proposed as described in Patent Document 1 below.
A glass substrate used for electronic devices such as a flat panel display and a solar cell is subjected to various treatments associated with electronic device production, such as a treatment for providing a film such as a transparent conductive film and a washing treatment. However, when a glass film is used as a glass substrate for those electronic devices, the glass film breaks easily due to even a slight stress change, because glass is a brittle material. Thus, there is a problem in that the handling of the glass film is very difficult, when the above-mentioned various treatments associated with electronic device production are carried out. In addition, there is another problem in that a glass film having a thickness of 200 μm or less is rich in flexibility, and hence the positioning of the glass film is difficult when the treatments associated with production are carried out, and displacement or the like in patterning may occur.
Thus, in order to solve the above-mentioned problems, a laminate is proposed as described in Patent Document 2 below. Patent Document 2 below proposes a laminate in which a supporting glass substrate and a glass sheet are laminated via a pressure-sensitive adhesive layer that may be maintained almost stably even after its repeated use. According to such laminate, even if a glass sheet having less strength and rigidity by itself is used, the production of a liquid crystal display device may be carried out by sharing a conventional production line for a liquid crystal display device, and after completion of the production processes, the supporting glass substrate can be peeled. Further, thermal warpage or the like can be prevented from occurring to some extent because a glass substrate is used as a supporting member. In addition, such a problem in that the laminate is displaced when positioning and patterning during treatment associated with production is unlikely to be occurred, because the supporting member has a high rigidity.